Polyvinylchloride Composition with a DI(C4-C20)Alkyl Cyclohexane-1,4-Dicarboxylate Having High CIS Content

ABSTRACT

Provided is a cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate which exhibits superior plasticizing property for PVC resin. Instead of a phthalate- or terephthalate-based aromatic ester derivative, 60% or more cis-dimethyl cyclohexane-1,4-dicarboxylate is used as a starting material. The 60% or more cis-dimethyl cyclohexane-1,4-dicarboxylate is subjected to transesterification with (C4-C20) primary alcohol to prepare 60% or more cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate. 
     Methanol produced as a byproduct during the transesterification is removed and some of the primary alcohol, which is evaporated, is recycled. Thus prepared 60% or more cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate exhibits superior plasticizer characteristics, including good plasticizing efficiency for PVC resin, high absorption rate, good product transparency after gelling, less bleeding toward the surface upon long-term use, and the like.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 13/124,803, filed Oct. 16, 2009, which claimspriority to Korean Patent Application Nos. 10-2009-0063075 and KR10-2008-0101629, filed Jul. 10, 2009 and Oct. 16, 2008, respectively,each of which is incorporated herein by reference in their entirety

TECHNICAL FIELD

The present invention relates to a method for preparing 60% or morecis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate, which exhibitssuperior plasticizing property for polyvinyl chloride (PVC) resin.

Further, the present invention relates to a method for preparing 60% ormore cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate with high purityand high yield by minimizing side reactions.

That is to say, the present invention relates to a method for preparinghigher alkyl cyclohexane-1,4-dicarboxylate with higher purity withoutside reactions by transesterifying dimethylcyclohexane-1,4-dicarboxylate having a particular stereostructure with(C4-C20) higher alcohol, rather than using an aromatic compound such asphthalate and terephthalate derivatives as starting material, therebymaintaining the stereostructure.

More specifically, the present invention relates to a method forpreparing 60% or more cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylatewithout side reactions and with high purity through transesterificationof 60% or more cis-dimethyl cyclohexane-1,4-dicarboxylate as startingmaterial with one or more alcohol(s) selected from (C4-C20) primaryalcohol.

BACKGROUND ART

Phthalates, e.g. dibutyl, dioctyl or diisononyl phthalate, have beenvery frequently used as plasticizers for plastics such as polyvinylchloride (PVC). However, recently, health concerns about their use havebeen raised, and their use in toys or other products is increasinglycriticized. In some countries, their use is prohibited. It is knownthrough long-term animal studies that phthalates may induce peroxisomeproliferation, which may be the cause of liver cancer, in mice and rats.Accordingly, demand on alternative plasticizers, which are safe forhumans and the environment, is on the increase.

As an alternative, di(C6-C12)alkyl cyclohexanoate-based plasticizers areevaluated as an eco-friendly and safe material without toxicity. Theyare obtained by first preparing phthalate plasticizers or terephthalateplasticizers and then converting them to cyclohexanes through additionof hydrogens to the benzene ring of the plasticizer. However, accordingto the method, since the cyclohexanoate-based plasticizer is prepared bydirect hydrogenation after preparing the high-molecular-weightterephthalate plasticizer having (C6-C12)alkyl groups, the hydrogenationof the benzene ring is relatively difficult due to the steric hindranceby the long high-molecular-weight aromatic chain and the high viscosityof the reaction solution. As a result, a more vigorous reactioncondition is required to solve the difficulties of the hydrogenation,which increases the risk of side reactions, including the breakage ofthe long carbon chain, decomposition or reduction of ester groups, etc.,thereby reducing product purity. Further, since it is impossible tocontrol an isomer of the cis/trans content of the resultantcyclohexanoate, it is difficult to selectively prepare the 60% or morecis-dimethyl cyclohexane-1,4-dicarboxylate desired by the presentinvention.

Korean Patent No. 10-0635396 proposes a use of cyclohexane-1,3- and-1,4-dicarboxylic acid derivatives as a plastic plasticizer, anddiscloses a material prepared by hydrogenation of isophthalate andterephthalate, and a preparation method thereof. However, since theabove-mentioned patent describes on the hydrogenation, which isperformed on terephthalate, the afore-said problem remains.

DISCLOSURE Technical Problem

After testing physical properties of 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate as a plasticizer for PVC resin, theinventors of the present invention have found out that it exhibitssuperior plasticizing property for PVC resin. They have found out thatdi(C4-C20)alkyl cyclohexane-1,4-dicarboxylate shows differentplasticizing property depending on the cis/trans contents. Especially,they have found out that the plasticizing effect is very superior whenthe cis content is 60% or more.

However, at present, cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylateis not available in commercial scale. Through consistent researches onthe preparation of 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate, the inventors have developed acommercially available method for stably preparing 60% or morecis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate without side reactionsand with superior yield.

The inventors have developed a simple process of preparing 60% or morecis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate without side reactionsand with high purity by reacting 60% or more cis-dimethylcyclohexane-1,4-dicarboxylate with a (C4-C20) primary alcohol undernormal pressure, without a process of hydrogenating dialkylterephthalate under high temperature and high pressure as an existingtechnique.

Accordingly, an object of the present invention is to provide a novelmethod for preparing 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate which exhibits superior plasticizingproperty for PVC resin.

Technical Solution

The present invention provides a method for preparing 60% or morecis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate by subjecting 60% ormore cis-dimethyl cyclohexane-1,4-dicarboxylate as a starting materialto transesterification with one or more alcohol(s) selected from(C4-C20) primary alcohol, rather than using phthalate or terephthalatederivatives as starting materials, in a reactor in the presence of acatalyst in order to prepare a di(C4-C20)alkyl ester compound of acyclohexane structure, as shown in Scheme 1.

The methanol byproduct produced during the process may be removed afterbeing condensed at a condenser equipped at the upper portion of thereactor. Another condenser may be equipped between the reactor and thecondenser to condense some of the (C4-C20) primary alcohol, which isevaporated, and introduce it again into the reactor. A purificationtower may be used instead of the condenser. A purification tower (whichmay or may not include an additional heat source supply system) operatedwith a reflux ratio of 0.1-20 may be equipped at the upper portion ofthe reactor, so that methanol is separated and removed from the primaryalcohol at the upper portion and the purified primary alcohol isrecovered and introduced again into the reactor at the lower portion.

Unless the methanol byproduct is removed at the condenser at the upperportion and the higher primary alcohol reactant is condensed between thecondenser and the reactor and introduced again into the reactor, thedesired di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate with high puritymay not be obtained because of decreased reaction purity, and the costfor purification may increase.

In scheme 1, R represents (C4-C20)alkyl.

The 60% or more cis-dimethyl cyclohexane-1,4-dicarboxylate which is usedas a starting material in the present invention is advantageous in thatno hydrogenation process is required because the benzene ring issaturated with hydrogen. The 60% or more cis-dimethylcyclohexane-1,4-dicarboxylate may have a cis content of 60-90%, morepreferably, 70-90%.

The 60% or more cis-dimethyl cyclohexane-1,4-dicarboxylate and the(C4-C20) primary alcohol are used in a molar ratio of 1:2 to 1:4.Outside the range, the primary alcohol may be evaporated duringtransesterification and unreacted dimethyl cyclohexane-1,4-dicarboxylatemay remain. Or, a large amount of unreacted primary alcohol may remainafter the reaction is completed, and it a lot of time may be required toremove them.

The (C4-C20) primary alcohol may be derived from a (C4-C20) saturatedhydrocarbon. Examples may include n-butyl alcohol, isobutyl alcohol,isoheptyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, isodecylalcohol, 2-propylheptyl alcohol, and the like, but not limited thereto.

The catalyst used in the present invention is added to facilitate thetransesterification. It may be used in an amount of 0.01 to 1.0 wt %,more preferably 0.05 to 0.5 wt %, based on the 60% or more cis-dimethylcyclohexane-1,4-dicarboxylate. If the catalyst is used in an amount lessthan 0.01 wt %, the reaction may not proceed well. And, an amountexceeding 1.0 wt % is uneconomical because the reaction rate and yielddo not increase in proportion to the addition amount of the catalyst.

The catalyst is one capable of facilitating transesterification, and maybe one or more selected from a group consisting of organometals such astetra(C3-C10)alkyl titanate and polymers thereof, metal salts such asaluminum sulfate, lithium fluoride, potassium chloride, cesium chloride,calcium chloride, iron chloride, aluminum phosphate, potassiumcarbonate, etc., metal oxides such as heteropoly acid, etc.,natural/synthetic zeolites, cation/anion exchange resins, and acidcatalysts such as sulfuric acid, hydrochloric acid, phosphoric acid,nitric acid, p-toluenesulfonic acid, methanesulfonic acid, alkylsulfate, etc. Among them, one or more selected from a group consistingof tetraisopropyl titanate, tetra-n-butyl titanate, tetraoctyl titanateand a mixture thereof may be preferably used.

In the present invention, the transesterification is carried out at 140to 220° C. for 2 to 6 hours. Once the reaction begins,transesterification occurs between the 60% or more cis-dimethylcyclohexane-1,4-dicarboxylate and the primary alcohol. During theprocess, methanol is produced as byproduct. The methanol byproduct needsto be removed continuously from the reactor through distillation for thereaction to proceed stably. When methanol is evaporated above a certaintemperature, the primary alcohol may be evaporated together. Therefore,the primary alcohol needs to be separated from methanol and recycled tothe reactor. By continuously separating the primary alcohol which isdistilled along with methanol and recycling it to the reactor, thecontent of the primary alcohol consumed in the reaction and the reactionpurity may be maintained.

In the present invention, in order to remove the methanol byproductproduced during the transesterification and to recycle the partiallyevaporated primary alcohol to the reactor, methanol is condensed andremoved by a condenser equipped at the upper portion of the reactor andthe partially evaporated primary alcohol is condensed and recycled tothe reactor by another condenser equipped between the reactor and thecondenser. Further, as described above, a purification tower may be usedinstead of the condenser. A purification tower (which may or may notinclude an additional heat source supply system) operated with a refluxratio of 0.1-20 may be equipped at the upper portion of the reactor, sothat methanol is separated and removed from the primary alcohol at theupper portion and the purified primary alcohol is recovered andintroduced again into the reactor at the lower portion.

The reactor that may be used for the transesterification of the presentinvention includes a batch reactor, a mixed flow reactor, a tubularreactor, etc., but not limited thereto.

A process for preparing 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate in accordance with the present inventionis illustrated in FIG. 1. Referring to FIG. 1, reaction byproductmethanol ({circle around (6)}) produced in a reactor ({circle around(1)}) where transesterification occurs and partially evaporated primaryalcohol are condensed and phase-separated by a primary condenser({circle around (2)}) maintained at an adequate temperature. Thusseparated liquid primary alcohol ({circle around (7)}) is recycled intothe reactor and subjected to transesterification, and gaseous methanol({circle around (8)}) is transferred to a secondary condenser ({circlearound (3)}), where it is condensed into liquid and removed to a vessel({circle around (11)}). In case a purification tower is used instead ofthe condenser ({circle around (2)}) in order to attain higher methanolseparation efficiency, a purification tower (which may or may notinclude an additional heat source supply system) operated with a refluxratio of 0.1-20 is equipped to separate methanol from the primaryalcohol. Methanol is separated at the upper portion and transferred tothe secondary condenser ({circle around (3)}). After being condensedthere, some of the methanol is recycled to the purification tower andthe remaining is separated. At the lower portion of the purificationtower, the purified primary alcohol is recovered and introduced againinto the reactor.

Methanol boils at 64.6° C., whereas the primary alcohol used in thereaction has a much higher boiling point. For example, 2-ethylhexylalcohol boils at 183° C. and isononyl alcohol boils at 203° C. However,within the reaction temperature range of 140-220° C., some of theprimary alcohol is evaporated together with methanol. The evaporation ofthe primary alcohol results in a significant change of the proportion ofreactants in the reactor and it becomes difficult to maintain a stablereaction. Thus, the evaporated primary alcohol ({circle around (7)})needs to be separated and recycled to the reactor. In order toeffectively perform this, two condensers are equipped at the upperportion of the reactor. That is, a primary condenser is equipped at theupper portion of the reactor, and a secondary condenser is equipped tocondense the gas that has passed through the primary condenser. Theprimary condenser condenses and separates the primary alcohol and thenrecycles it to the reactor. The secondary condenser condensed methanolinto liquid and separates it. The primary condenser which condensed theprimary alcohol is maintained at a temperature range of 70-180° C.,which is higher than the boiling point of methanol and lower than theboiling point of the primary alcohol. A temperature range of 90-150° C.may be more preferable. And, the secondary condenser which needs tocondense the entire amount of the gaseous methanol that has passedthrough the primary condenser is maintained in a temperature range of60° C. or below, which is lower than the boiling point of methanol. Atemperature range of 40° C. or lower may be more preferable.

When the transesterification continues for 2-6 hours, the reaction iscompleted and no more methanol is produced. When the reaction iscompleted, unreacted primary alcohol and catalyst remain in the reactionsolution in addition to the desired 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate. Therefore, a post-treatment is carriedout to remove them. The reaction solution ({circle around (9)}) istransferred to a post-treatment tank ({circle around (4)}) forpost-treatment.

The post-treatment process will be described hereinafter.

The post-treatment includes the processes of decomposition of thecatalyst, removal of unreacted primary alcohol and filtration ofimpurities. The catalyst remaining after the completion of thetransesterification, e.g. titanate-based catalyst, is decomposed intotitanium oxide and saturated hydrocarbon (propane, butane, etc.) uponcontact with water. Thus, a small amount of water or steam is added tothe reaction solution to decompose the catalyst.

When the catalyst is completely decomposed, the reaction solution in thereactor is heated to 200° C. or above and the unreacted primary alcoholis completely removed under reduced pressure ({circle around (4)}).After the unreacted primary alcohol is removed, an adsorbent is added tothe reaction solution ({circle around (10)}) to remove suspendedimpurities. Further, an alkaline adsorbent may be added to remove acidicimpurities that may be produced during the reaction. Following stirringand filtration ({circle around (5)}), purified, high-purity 60% or morecis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate ({circle around (12)})may be obtained.

The alkaline adsorbent may be one or more selected from a groupconsisting of MgO/Cl/SO₄, MgO/SiO₂/Cl/SO₄, MgO/Al₂O₃/SiO₂/Cl/SO₄,MgO/Al₂O₃/SiO₂/CO₂/Cl/SO₄ and hydrates thereof. By using the alkalineadsorbent, it is possible to remove the acidic impurities included inthe 60% or more cis-dimethyl cyclohexane-1,4-dicarboxylate used as thestarting material and remaining after the completion of the reaction,and to remove such acidic substances as carboxylic acid generated fromthe hydrolysis of the reaction product 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate by the water or steam added to decomposethe catalyst.

In addition, the acidic impurities generated due to contact with waterduring the transesterification need to be removed through apost-treatment process. When the reaction is performed by introducing60% or more cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate as thestarting material, catalyst and primary alcohol even after the reactoris purged using steam and then dried, a trace amount of water remains inthe reactor, which may lead to the hydrolysis of the starting materialor the reaction product, thereby increasing the acid value. Therefore,the acidic impurities generated from the starting material need to beremoved during the reaction or post-treatment using an alkalineadsorbent.

The 60% or more cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylateprepared in accordance with the present invention includesdi(n-butyl)cyclohexane-1,4-dicarboxylate,di(isobutyl)cyclohexane-1,4-dicarboxylate,di(isoheptyl)cyclohexane-1,4-dicarboxylate,di(2-ethylhexyl)cyclohexane-1,4-dicarboxylate,di(isononyl)cyclohexane-1,4-dicarboxylate,di(isodecyl)cyclohexane-1,4-dicarboxylate,di(2-propylheptyl)cyclohexane-1,4-dicarboxylate, etc. Thedi(C4-C20)alkyl cyclohexane-1,4-dicarboxylate has a cis content of 60%or more, preferably 60-90%, more preferably 70-90%.

-   -   <cis-DMCD→cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate>

-   -   <trans-DMCD→trans-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate>

Advantageous Effects

Surprisingly, the 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate prepared in accordance with the presentinvention exhibits very superior plasticizing property for PVC resin.Further, it has superior plasticizer characteristics, including fastplasticizer absorption for PVC resin, good product transparency aftergelling, less bleeding toward the surface upon long-term use, and thelike.

DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from the following description ofpreferred embodiments given in conjunction with the accompanyingdrawings, in which:

FIG. 1 schematically shows the process of transesterification.

FIG. 2 is a graph showing change of temperature duringtransesterification ({circle around (a)}): Temperature of reactionsolution (FIG. 1 {circle around (1)}), ({circle around (b)}) Temperatureof primary condenser (FIG. 1 {circle around (2)}), {circle around (c)}:Temperature of gas introduced to secondary condenser (FIG. 1 {circlearound (8)})).

FIG. 3 shows GC analysis result of cis/trans contents of the products ofExample 2 and Comparative Example 2((a)1,4-DEHCH prepared using 81%cis-DMCD, (b)1,4-DEHCH prepared using 97% trans-DMCD).

FIG. 4 shows the change of the surface of the sheets of Examples 4-6 andComparative Examples 4-6 kept at 80° C. for 10 days.

BEST MODE

Hereinafter, the examples and experiments will be described to helpunderstand the present invention. The following examples and experimentsare for illustrative purposes only and are not intended to limit thescope of the present invention.

Example 1 Preparation of di(isononyl)cyclohexane-1,4-dicarboxylate(1,4-DINCH)

Isononyl alcohol (8.1 mol), dimethyl cyclohexane-1,4-dicarboxylate(DMCD, c is 81.8%, trans 18.2%, SK NJC, 3.0 mol) and tetraisopropyltitanate catalyst (0.85 g) were added to a 2.5 L reactor equipped with astirrer and two condensers and heated to 185° C. Transesterification wascarried out for 6 hours under nitrogen atmosphere. Methanol, which wasproduced as reaction byproduct, was evaporated inside the reactor,collected as liquid while passing through the two condensers, and thenremoved.

The transesterification was started when the temperature reached 185° C.As the methanol byproduct was produced, the temperatures at the primarycondenser and the inlet of the secondary condenser increased rapidly[FIG. 2]. In order to reduce the loss of isononyl alcohol while methanolwas removed, the temperature of the primary condenser was maintained at150° C. or below and the temperature of the inlet of the secondarycondenser was maintained at 100° C. or below.

Nitrogen was supplied to aid the removal of the methanol byproduct andblock the inflow of air from outside. Nitrogen was supplied at a rate of0.4 L/min for the first two hours following the initiation of reaction,and at a rate of 0.8 L/min thereafter.

After the reaction was completed, the reaction solution was transferredto a post-treatment tank ({circle around (4)}) and cooled to 80° C.After adding deionized water (45 g), the tetraisopropyl titanatecatalyst was decomposed by strong stirring for 5 minutes. After furtheradding activated carbon (0.45 g) and an alkaline adsorbent (Kyowaad-600,Kyowa Chemical, 0.90 g), stirring was carried out for 5 minutes.Subsequently, unreacted isononyl alcohol was removed at 200° C. underreduced pressure using a vacuum pump. The reaction product was cooled to120° C. and filtered. Di(isononyl)cyclohexane-1,4-dicarboxylate (cis81%, trans 19%) was obtained with a purity of 99.2%.

Example 2 Preparation of di(2-ethylhexyl)cyclohexane-1,4-dicarboxylate(1,4-DEHCH)

2-Ethylhexyl alcohol (8.1 mol), dimethyl cyclohexane-1,4-dicarboxylate(DMCD, c is 81.8%, trans 18.2%, SK NJC, 3.0 mol) and tetraisopropyltitanate catalyst (0.85 g) were added to a 2.5 L reactor equipped with astirrer and two condensers and heated to 180° C.Di(2-ethylhexyl)cyclohexane-1,4-dicarboxylate (cis 81%, trans 19%) wasobtained with a purity of 99.3% in the same manner as in Example 1.

Example 3 Preparation of di(2-propylheptyl)cyclohexane-1,4-dicarboxylate(1,4-DPHCH)

2-Propylheptyl alcohol (8.1 mol), dimethylcyclohexane-1,4-dicarboxylate(DMCD, c is 81.8%, trans 18.2%, SK NJC, 3.0 mol) and tetraisopropyltitanate catalyst (0.85 g) were added to a 2.5 L reactor equipped with astirrer and two condensers and heated to 185° C.Di(2-propylheptyl)cyclohexane-1,4-dicarboxylate (cis 81%, trans 19%) wasobtained with a purity of 99.3% in the same manner as in Example 1.

Comparative Example 1 Preparation ofdi(isononyl)cyclohexane-1,4-dicarboxylate

Isononyl alcohol (8.1 mol), dimethylcyclohexane-1,4-dicarboxylate (DMCD,c is 1.7%, trans 98.3%, Eastman, 3.0 mol) and tetraisopropyl titanatecatalyst (0.85 g) were added to a 2.5 L reactor equipped with a stirrerand two condensers and heated to 185° C.Di(isononyl)cyclohexane-1,4-dicarboxylate (cis 3%, trans 97%) wasobtained with a purity of 99.7% in the same manner as in Example 1.

Comparative Example 2 Preparation ofdi(2-ethylhexyl)cyclohexane-1,4-dicarboxylate

2-Ethylhexyl alcohol (8.1 mol), dimethylcyclohexane-1,4-dicarboxylate(DMCD, c is 1.7%, trans 98.3%, Eastman, 3.0 mol) and tetraisopropyltitanate catalyst (0.85 g) were added to a 2.5 L reactor equipped with astirrer and two condensers and heated to 180° C.Di(2-ethylhexyl)cyclohexane-1,4-dicarboxylate (cis 3%, trans 97%) wasobtained with a purity of 99.8% in the same manner as in Example 1.

Comparative Example 3 Preparation ofdi(2-propylheptyl)cyclohexane-1,4-dicarboxylate

2-Propylheptyl alcohol (8.1 mol), dimethylcyclohexane-1,4-dicarboxylate(DMCD, c is 1.7%, trans 98.3%, Eastman, 3.0 mol) and tetraisopropyltitanate catalyst (0.85 g) were added to a 2.5 L reactor equipped with astirrer and two condensers and heated to 185° C.Di(2-propylheptyl)cyclohexane-1,4-dicarboxylate (cis 3%, trans 97%) wasobtained with a purity of 99.8% in the same manner as in Example 1.

For the 60% or more cis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylatederivatives prepared in accordance with the present invention, a fasterabsorption rate in polyvinyl chloride (PVC) resin is preferred becausethe time required for mixing with PVC can be reduced. Viscosity andabsorption rate in PVC resin of the di(C4-C20)alkylcyclohexane-1,4-dicarboxylate derivatives prepared in Examples 1 to 3and Comparative Examples 1 to 3 depending on cis/trans contents aresummarized in Table 1. The plasticizer absorption rate was evaluated bycomparatively measuring the times required for the plasticizer to becompletely absorbed in PVC resin (P-1000, Hanwha Chemical). A planetarymixer (Brabender) was used for the measurement. After adding 400 g ofP-1000 resin in the mixer maintained at 80° C., the resin temperaturewas uniformly increased to 80° C. while stirring. Subsequently, 50 phrof the plasticizer was added to the resin, which was being stirred. Withthe addition of the plasticizer, the load of the mixer blade increases.However, as the plasticizer is absorbed, the powder fluidity increasesand the load decreases gradually. The plasticizer absorption rate wasevaluated by measuring the time ranging from the point where the loadbegan to increase to the point where it decreased.

TABLE 1 Cis 81%, trans 19% Cis 3%, trans 97% Vis- Absorption Vis-Absorption cosity rate in PVC Comparative cosity rate in PVC Examples(25° C.) resin Examples (25° C.) resin 1,4- 40 cP 412 sec 1,4-DINCH 43cP 648 sec DINCH (Comp. (Ex. 1) Ex. 1) 1,4- 28 cP 270 sec 1,4-DEHCH 30cP 338 sec DEHCH (comp. (Ex. 2) Ex. 2) 1,4- 44 cP 782 sec 1,4-DPHCH 48cP 836 sec DPHCH (Comp. (Ex. 3) Ex. 3)

As seen in Table 1, the higher the cis content was, the lower theviscosity was and the faster the absorption rate in PVC resin was. Thatis, the high-cis plasticizer according to the present invention exhibitsvery superior processability and absorption rate in PVC resin.

Examples 4-6 and Comparative Examples 4-6 Comparison of Performance asPlasticizer (I)

In order to compare the performance of di(C4-C20)alkylcyclohexane-1,4-dicarboxylate derivatives prepared in accordance withthe present invention as plasticizer depending on cis/trans contents,PVC blends were prepared with the compositions and mixing proportionspresented in Table 2. 0.8 mm sheets were formed by uniformly mixing in amixing roll maintained at 160° C. for 4 minutes.

Thus prepared three sheets were stacked and pressed for 10 minutes usinga press forming machine at 180° C. 2 mm-thick, transparent, soft PVCsheets were obtained.

TABLE 2 (Unit: parts by weight) Ex. 4 Ex. 5 Ex. 6 Comp. Ex. 4 Comp. Ex.5 Comp. Ex. 6 PVC resin (P-1000) 100 100 100 100 100 100 Plasticizer cis81%, 1,4-DINCH 50 — — — — — trans 19% (Ex. 1) 1,4-DEHCH — 50 — — — —(Ex. 2) 1,4-DPHCH — — 50 — — — (Ex. 3) cis 3%, 1,4-DINCH — — — 50 — —trans 97% (Comp. Ex. 1) 1,4-DEHCH — — — — 50 — (Comp. Ex. 2) 1,4-DPHCH —— — — — 50 (Comp. Ex. 3) KBZ-290G 2.5 2.5 2.5 2.5 2.5 2.5 E-700 2.0 2.02.0 2.0 2.0 2.0  P-1000: PVC resin (Hanwha Chemical)  KBZ-290G:Ba/Zn-based PVC stabilizer (Kolon Petrochemical)  E-700: Epoxylatedsoybean oil stabilizer (Songwon Industrial)

In order to compare the degree of effluence of the plasticizer to thesheet surface, the transparent sheets obtained above were kept at 80° C.for 10 days and the sheet surface was observed using a microscope. Asseen in FIG. 4, staining due to the effluence of the plasticizer to thesheet surface was severer as the number of carbon atoms of the primaryalcohol increased (C8<C9<C10). The degree of effluence was much severerin high-trans sheets (Comparative Examples 4, 5 and 6) than in thehigh-cis sheets (Examples 4, 5 and 6). Particularly, the difference waslarger as the number of carbon atoms increased. For soft PVC productsincluding a plasticizer to maintain appropriate properties and qualitiesfor a long period of time, they should have good durability with noquality change and plasticizer effluence under various use environments.It was confirmed that high-cis plasticizers are more adequate thanhigh-trans plasticizers, in this regard.

The change of bleeding at the sheet surface of the PVC sheets ofExamples 4-6 and Comparative Examples 4-6 depending on cis/transcontents was measured by light transmittance and haze. Lighttransmittance and haze were measured using Haze-Gard Plus (BYK Gardner).

The PVC sheets prepared in Examples 4-6 and Comparative Examples 4-6were kept at 80° C. for 10 days, and the change of light transmittanceand haze was measured. The result is given in Table 3.

TABLE 3 Plasticizer cis 81%, trans 19% cis 3%, trans 97% 1,4-DINCH1,4-DEHCH 1,4-DPHCH 1,4-DINCH 1,4-DEHCH 1,4-DPHCH Sheet Ex. 4 Ex. 5 Ex.6 Comp. Ex. 4 Comp. Ex. 5 Comp. Ex. 6 Light Before 92.3 92.8 91.8 92.292.7 90.5 transmittance After 81.1 83.7 76.0 78.6 81.9 71.9 (%) Haze (%)Before 0.77 0.56 1.36 0.77 0.65 2.86 After 2.65 1.38 7.87 11.00 1.715.17

As seen in Table 3, the higher the cis content, the higher is the lighttransmittance and the lower the haze. Before heat treatment, the lighttransmittance of the transparent sheet was similar (91-92%) withoutregard to the primary alcohol or the cis/trans contents of thecyclohexane-1,4-dicarboxylate derivatives. The haze of the sheet wasalso in the range from 0.5 to 2.9%. After the treatment at 80° C. for 10days, the light transmittance of the high-cis samples (Examples 4-6)decreased to 76-84%, whereas that of the high-trans samples (ComparativeExamples 4-6) decreased more to 72-82%. The change of haze showed asimilar pattern to that of the light transmittance. Especially,Comparative Example 6 showed a low haze of 5.17%, which was due to theformation of an oily film on the sheet surface caused by the bleeding ofthe plasticizer.

The softness of the PVC sheets of Examples 4-6 and Comparative Examples4-6 was measured using a durometer. The higher the plasticizing effectof the plasticizer for PVC resin, the softer is the sheet and the lowerthe hardness. The hardness of the sheet was measured based on the ShoreA scale. The result is given in Table 4. For the same di(C4-C20)alkylcyclohexane-1,4-dicarboxylate derivatives, the high-cis derivatives(Examples 4-6) exhibited a plasticizing effect 1.7-4.5% better than thehigh-trans derivatives (Comparative Examples 4-6). A better plasticizingeffect provides advantages in use because the same softness can beobtained with less amount.

TABLE 4 Hardness (Shore A) of PVC samples depending on cis/transcontents Examples Ex. 4 Ex. 5 Ex. 6 cis 81%, trans 19% 1,4-DINCH1,4-DEHCH 1,4-DPHCH 85.5 82.0 87.5 Comparative Examples Comp. Ex. 4Comp. Ex. 5 Comp. Ex. 6 cis 3%, trans 97% 1,4-DINCH 1,4-DEHCH 1,4-DPHCH89.5 84.5 89.0 Difference of hardness 4.5% 3.0% 1.7%

Examples 7-9 and Comparative Examples 7-9 Comparison of Performance asPlasticizer (II)

In order to compare the performance of the di(C4-C20)alkylcyclohexane-1,4-dicarboxylate derivatives prepared in accordance withthe present invention as plasticizer for paste PVC resin depending oncis/trans contents, PVC resin and additives were mixed as in Table 5.Physical properties, gelling property and foaming property of theresultant paste sols were compared in Table 6.

TABLE 5 Composition Ex. 7 Ex. 8 Ex. 9 Comp. Ex. 7 Comp. Ex. 8 Comp. Ex.9 Paste resin (EL-103) 100 100 100 100 100 100 Plasticizer cis 81%,1,4-DINCH 70 — — — — — trans 19% (Ex. 1) 1,4-DEHCH — 70 — — — — (Ex. 2)1,4-DPHCH — — 70 — — — (Ex. 3) cis 3%, 1,4-DINCH — — — 70 — — trans 97%(Comp. Ex. 1) 1,4-DEHCH — — — — 70 — (Comp. Ex. 2) 1,4-DPHCH — — — — —70 (Comp. Ex. 3) CNA070 3.0 3.0 3.0 3.0 3.0 3.0 DWPX03MB 2.0 2.0 2.0 2.02.0 2.0 TiO₂ 10 10 10 10 10 10 OM-10 90 90 90 90 90 90 BYK-5110 3.0 3.03.0 3.0 3.0 3.0  CNA070: Na/Zn-based PVC stabilizer (CNA)  DWPX03MB:ADCA-based foaming agent (Dongjin Semichem)  OM-10: Calcium carbonate(Omiya Korea)  BYK-5110: Viscosity reducing agent (BYK)

TABLE 6 Plasticizer cis 81%, trans 19% cis 3%, trans 97% 1,4-DINCH1,4-DEHCH 1,4-DPHCH 1,4-DINCH 1,4-DEHCH 1,4-DPHCH Sheet Ex. 7 Ex. 8 Ex.9 Comp. Ex. 7 Comp. Ex. 8 Comp. Ex. 9 Sol viscosity 3,850 3,450 3,7004,350 3,500 4,300 Gelling property Δ ◯ Δ Δ ◯ Δ Foaming property Δ ◯ Δ Δ◯ Δ ◯: good, Δ; moderate, X: poor

The paste sols prepared using high-cis plasticizers (Examples 7-9) had alower viscosity than the sols prepared using high-trans plasticizers(Comparative Examples 7-9). Thus, they exhibited better formingworkability, processability, and the like. Gelling property and foamingproperty were comparable.

The present application contains subject matter related to Korean PatentApplication Nos. 10-2008-0101629 and 10-2009-0063075, filed in theKorean Intellectual Property Office on Oct. 16, 2008 and Jul. 10, 2009,the entire contents of which are incorporated herein by reference.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

INDUSTRIAL APPLICABILITY

The method for preparing 60% or more cis-di(C4-C20)alkylcyclohexane-1,4-dicarboxylate according to the present invention iseconomical because no hydrogenation process is required. The methanolbyproduct produced during the transesterification can be easily removedbecause it has a low boiling point. The reaction proceeds fast, and noneutralization treatment is required for removal of unreacted materialsafter completion of the reaction. Since the side reactions areprevented, the product can be obtained with high purity. In addition,since a post-treatment process is simply performed by filtering offimpurities by adsorption without generation of waste water, the processis environment-friendly. Therefore, highly pure 60% or morecis-di(C4-C20)alkyl cyclohexane-1,4-dicarboxylate can be preparedthrough a simple and commercial-scale process. Further, the recoveredmethanol can be recycled for the preparation of 60% or more cis-dimethylcyclohexane-1,4-dicarboxylate or for other purposes through a simplepurification process.

1. A polyvinyl chloride (PVC) composition comprising di(C4-C20)alkylcyclohexane-1,4-dicarboxylate having a cis content of 60-90%.